Yes the iPhone software version 2.0 has been leaked! You can download it directly from Apple here:
iPhone 2.0 IPSW. To install, download iTunes 7.7 and use cmd+update/ctrl+update to select the firmware in iTunes. This firmware version will be erasing your entire phone! This is most likely to expand the OS partition for applications available through App Store. With all 1.x updates normally the Media partition is left alone because the OS partition does not change size, but in this case iTunes will be making a full backup of the Media partition for this update. I have been told by a few sources this firmware update is not downgradable even with DFU mode. Though I don't believe it to be true, update at your own risk!
Max